<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div id="father">
  <h1>标题</h1>
  <p id="p1">p1</p>
  <p class="p2">p2</p>
</div>

<script>
  //对应css的选择器
  var h1=document.getElementsByTagName('h1');
  var p1=document.getElementById("p1");
  var p2=document.getElementsByClassName("p2");
  var father=document.getElementById('father')

  var childs=father.children; //获取父节点下面的所有子节点
  //father.firstChild
  //father.lastChild
</script>
</body>
</html>